Auditory Brainstem response electrophysiological thresholds with narrow band chirps stimuli in hearing infants

Objectives: to describe reference values for the electrophysiological thresholds obtained in the frequency-specific Auditory Brainstem Response (fsABR) with the NB CE-Chirp (R) LS and NB iChirp stimuli in hearing infants and to compare the variables: Minimum Levels of Response (MLR), latency, amplitude and examination time.Methods: the sample consisted of 74 full-term infants, with a mean age of 23.11 days, 29 females and 45 males. The participants underwent fsABR at the frequencies of 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz, to measure the MLR with the NB CE-Chirp (R) LS stimulus in the Eclipse equipment, and with the NB iChirp stimulus in the SmartEP, all in natural sleep and performed in the same session. The waveforms were evaluated by judges and later, for the comparison of thresholds and examination time, analyzed with the Wilcoxon test. To compare latency and amplitude, the Student's T Test and ANOVA were used for the same variables, but with the same stimulus. The Kruskal-Wallis test was used to compare the examination time at the different frequencies.Results: The MLR and latency at 500 Hz and 1000 Hz showed a statistically significant difference between the stimuli, with lower thresholds and higher latencies for the NB iChirp. Higher amplitudes were obtained with the NB iChirp stimulus. The average examination time for the threshold investigation in the four frequencies was 40 min for each ear.Conclusion: it was possible to present reference values for the MLR and latencies for the NB CE-Chirp (R) LS and NB iChirp stimuli for hearing infants. In addition, with the NB iChirp, the latency of the responses was influenced by the frequency, but it was the stimulus that provided greater amplitudes. With the NB CE-Chirp (R) LS, the fre-quency did not influence latency, except at 500 Hz, and the stimulus provided recordings that facilitated the visualization of wave V. There was no difference in the examination time between the stimuli, nor between the test frequencies.